This invention relates to a method and apparatus for pipeline renovation, and more particularly to the internal renovation of liquid-carrying pipelines.
It is well known that, over a period of time, liquid-carrying pipelines can suffer internal corrosion and breakdown which can result, for example, in leaks and in contamination of the liquid passing therethrough. Since complete replacement of a pipeline can be extremely expensive, attempts have been made to renovate older pipelines by providing an internal lining therein to cover the internal wall and keep the liquid out of contact therewith. In the water industry, linings have been provided in a number of ways.
In one technique, a process known as inversion is used. An inverted lining is formed by allowing a flexible cylindrical liner to be turned inside out within the pipeline, and pressed radially outwardly against the inside wall of the pipeline. The inverted liner has a resin coating on its outer surface, and as the inverted liner is pressed against the inside wall of the pipeline, the liner becomes bonded by the resin to the inner wall of the pipeline. Inversion of the cylindrical liner can be effected by air or water, as will be understood by those skilled in the art. These linings, when cured, are semi-structural.
Whilst the inversion technique has proved satisfactory, there is a disadvantage especially when lining water mains in that organic compounds from the resin can permeate the liner and contaminate the water supply. Because of this, inverted linings require lengthy and expensive testing before their safety for use in contact with potable water can be ensured.